Thin films of ferroelectric materials are being investigated for a wide variety of electrical and optical applications. There are several reasons for the increasing importance of ferroelectric thin films:
The trend toward miniaturization of electronic components has led to the development of thin film ferroelectric devices performing the same electronic function with only a fraction of the volume of devices based on bulk ceramic or single-crystal elements.
Ferroelectric thin films are replacing expensive single crystal ferroelectrics. Thin films have added design advantages relative to single crystals: decreased volume and increased geometrical flexibility.
Applications are being identified that utilize new device concepts, exploiting properties that are unique to both thin films and ferroelectric materials.
Important ferroelectric materials for thin-film applications are typically titanates and niobates with oxygen-octahedral structure types, such as the perovskite structure. Examples of such ferroelectric perovskites include lead titanate (PbTiO.sub.3), lead zirconate (PbZrO.sub.3), lead zirconate titanate (Pb(Zr,Ti)O.sub.3 or PZT), lead lanthanum titanate ((Pb,La)TiO.sub.3), lead lanthanum zirconate ((Pb,La)ZrO.sub.3), lead lanthanum zirconate titanate ((Pb,La)(Zr,Ti)O.sub.3 or PLZT), lead magnesium niobate (Pb(Mg.sub.1/3 Nb.sub.170 )O.sub.3), lead zinc niobate (Pb(Zn.sub.1/3 Nb.sub.170 )O.sub.3), strontium titanate (SrTiO.sub.3), barium titanate (BaTiO.sub.3), strontium barium titanate ((Sr,Ba)TiO.sub.3), barium titanate zirconate (Ba(Ti,Zr)O.sub.3), potassium niobate (KNbO.sub.3). potassium tantalate (KTaO.sub.3), and potassium tantalate niobate (K(Ta,Nb)O.sub.3). Device applications of ferroelectric thin films require that bulk ferroelectric properties are achieved in thin films. The physical and chemical properties of the film (density, uniformity, stoichiometry, crystal structure, and microstructure) are extremely important. The utilization of ferroelectric thin films for electronic and optical applications has been hindered by the lack of a large-scale production process for the deposition of device-quality ferroelectric thin-films.